The present application is based on and claims priority under 35 U.S.C. xc2xa7119 with respect to Japanese Patent Application No-2001-079293 on Mar. 19, 2001 (13th Year of Heisei), the entire content of which is incorporated herein by reference.
1. Field of The Invention
The present invention is generally directed to a CO-shift device which shifts carbon monoxide into carbon dioxide.
2. Description of the Related Art
Japanese Patent Laid-open Publication No. 2000-302405 discloses such a CO-shift device. In this CO-shift device, the following chemical reaction occurs.
CO+H2O⇄H2+CO2+Q(Heat Generation)
For reacting CO effectively in the above-mentioned reaction formula, the reaction temperature is required to decrease. However, due to the heat generation reaction, as the reaction proceeds, the temperature is increased, resulting in difficulty in progress in the rightward direction in the above reaction formula.
In addition, lowering the reaction temperature causes the reaction speed to slow, and to avoid such a phenomena the CO-shift device has to be enlarged in capacity.
Moreover, the above-mentioned CO-shift device is provided at its downstream side with a heat exchanger, and the temperature in the CO-shift device is controlled to reduce CO effectively. However, such a structure makes the fuel cell system complicated.
Thus, a need exists to provide a CO-shift device which is free from the aforementioned drawbacks.
In accordance with a first aspect of the present invention, a CO-shift device comprises a main body having therein a space in which a CO-shift catalyst is accommodated, the space being divided into an inner space and an outer space surrounding the inner space; an inlet portion formed at one end portion of the inner space, the inlet portion being supplied with a reformed gas such that the reformed gas flows through the inner space; an outlet portion formed at one end portion of the outer space; and a redirecting portion provided between the other end portion of the inner space and the other end portion of the redirecting portion, thereby reversing the reformed gas flown into the other end of the inner apace in order that the resulting reformed gas passes through the outer space to be exhausted from the outlet portion, the reformed gas being shifted to reduce CO by the CO-shift catalyst during its movement through the inner and outer spaces.
In accordance with a second aspect, in a CO-shift device according to the first aspect, the main body is made up of a pair of inner and outer cylindrical members which have a common axis, the inner space being defined in the inner cylindrical member, the outer space being defined between the inner and outer cylindrical members.
In accordance with a third aspect, a CO-shift device according to the first aspect is modified such that the redirecting portion is free from catalyst installation.
In accordance with a fourth aspect, a CO-shift device according to the first aspect is modified such that the catalyst is supported by a set of a punched plate and a meshed plate, each of the holes of each of the plates being smaller than the catalyst particle diameter.
In accordance with a fifth aspect, a CO-shift device according to the first aspect is modified such that a heat-recovering device is provided which is in the form of a passage, the passage being formed on an outer surface of an outer wall of the main portion, for recovering a heat generated during CO-shift reaction by a coolant when the coolant passes through the passage.
In accordance with a sixth aspect, a CO-shift device according to the first aspect is modified such that a heat-recovering device is provided which is in the form of a passage, the passage being formed on an outer surface of an outer wall of the main portion, for recovering a heat generated during CO-shift reaction by a coolant when the coolant passes through the passage.